The goal of this project is to determine in what manner the cerebellum of weakly electric fish (Gymnotoidei) analyze sensory information received with the electric sense. The originally proposed studies can be divided into the following categories: 1. Electrophysiological study of the neural circuitry of the area of the cerebellar cortex known to process electrosensory information. 2. Identification of afferent electrosensory pathways to the cerebellum and identification of areas receiving output from the electrosensory area of the cerebellum. 3. Studies of cerebellar cells receiving input from multiple sensory modalities. 4. Studies of receptive fields of cerebellar cells. 5. Studies of the acuity or discrimination ability of the electrosensory system at many CNS levels including the cerebellum. The projects for the current year include continued electrophysiological studies of the cerebellar circuitry (category 1), studies of afferent and efferent cerebellar connections (category 2) and studies of the object detection abilities of the lateral line lobe (category 5). In addition to these, time was spent completing studies of electroreceptor properties in "pulse" type electric fish. This ancillary project was undertaken to provide basic information about peripheral aspects of electroreception in this category of electric fish so that central aspects of electroreception can also be studied in species having a pulse type electric organ discharge. BIBLIOGRAPHIC REFERENCES: Bastian, J.: The range of electrolocation: A comparison of electroreceptor responses and the responses of cerebellar neurons in a Gymnotid fish. J. Comp. Physiol. 108, 193-210 (1976). Bastian, J.: Frequency response characteristics of electroreceptors in "Pulse Type" electric fish. Sixth Annual Mtg., Society for Neurosciences. (1976) Abst. #12.